1. Field of the Invention
This invention relates to a method and apparatus for delivering electrical energy to a patient for maintaining and/or restoring the pumping rhythm of a heart, and more particularly to a method and apparatus for regulating a current flow to the patent to conform with a predetermined maximum value and/or according to a predetermined waveform. A single power source is provided to deliver current with either pacing or defibrillation energy.
2. Description of the Related Art
The frequent occurrence of sudden cardiac arrest (SCA) is well known. SCA occurs when the heart stops pumping blood, usually due to abnormal electrical activity in the heart, such as for example, ventricular fibrillation, which is caused very fast electrical activity in the heart. Ventricular fibrillation is treated by applying an electric shock to the patient's heart through the use of a defibrillator. Other forms of abnormal cardiac rhythms, such as bradycardia (slow heart rate) and tachycardia (rapid heart rate) may be treated with a low voltage pacing pulse, which assists the heart's natural pacemakers. Devices which accomplish both defibrillation and pacing typically include two power sources, two capacitors, and two control mechanisms, one for the high energy defibrillation pulse and one for the lower energy pacing pulses. This double circuitry ultimately increases the weight size, and cost of the device.
There is a need for an apparatus which performs both defibrillation and pacing and which uses a single power source, a single high energy capacitor and a single control mechanism to deliver either defibrillation or pacing energy.